Flexible carbon nanotube fibers woven into clothing collect precise ECG and heart rate

There’s no need to don smartwatches or uncomfortable chest straps to monitor your heart if your comfy shirt can do a better job.

This is the idea behind “smart clothing” developed by a laboratory at Rice University, which used its conductive nanotube yarn to weave functionality into ordinary clothing.

The laboratory of the Brown School of Engineering of the chemical and biomolecular engineer Matteo Pasquali reported in the journal of the American Chemical Society Nano letters that he sewed nanotube fibers into sportswear to monitor heart rate and take a continuous electrocardiogram (ECG) of the wearer.

The fibers are just as conductive as metallic threads, but washable, comfortable and much less likely to break when a body is in motion, according to the researchers.

Overall, the shirt they upgraded was better for data collection than a standard chest belt monitor taking live measurements during experiments. When paired with commercial medical electrode monitors, the carbon nanotube jacket gave slightly better ECGs.

“The shirt should fit snug against the chest,” said Lauren Taylor, a graduate student of Rice, the study’s lead author. “In future studies, we will focus on using denser patches of carbon nanotube threads so that there is more surface area to contact the skin.”

The researchers noted that the nanotube fibers are soft and flexible, and the clothes that incorporate them are machine washable. The fibers can be machine sewn into the fabric like standard thread. The zigzag stitching pattern allows the fabric to stretch without breaking it.

The fibers not only provided stable electrical contact with the wearer’s skin, but also served as electrodes to connect electronic devices such as Bluetooth transmitters to relay data to a smartphone or connect to a Holter monitor that can be stored in the bag. a user’s pocket, Taylor said.

Pasquali’s lab introduced carbon nanotube fiber in 2013. Since then the fibers, each containing tens of billions of nanotubes, have been studied to be used as bridges to repair damaged hearts, as electrical interfaces to the brain. , for use in cochlear implants, as flexible antennae, and for automotive and aerospace applications. Their development is also part of the Rice-based Carbon Hub, a multi-university research initiative led by Rice and launched in 2019.

The original nanotube filaments, measuring around 22 microns wide, were too thin to be handled by a sewing machine. Taylor said that a string maker was used to create a sewing thread, essentially three bundles of seven filaments each, woven into roughly the size of regular thread.

“We worked with someone who sells small machines designed to make ropes for model ships,” said Taylor, who first tried hand-weaving the yarn, with limited success. “He managed to make us a medium-scale device that does the same thing.”

She said the zigzag pattern can be adjusted to accommodate the likely stretch of a shirt or other fabric. Taylor said the team was working with Dr Mehdi Razavi and colleagues at the Texas Heart Institute to determine how to maximize skin contact.

The fibers woven into the fabric can also be used to integrate antennas or LEDs, according to the researchers. Minor modifications to the geometry of the fibers and associated electronics could potentially allow the clothing to monitor vital signs, exertion or respiratory rate.

Taylor noted that other potential uses could include human-machine interfaces for automobiles or soft robotics, or as antennas, health monitors, and ballistic protection in military uniforms. “We demonstrated with a collaborator a few years ago that carbon nanotube fibers dissipate energy better by weight than Kevlar, and that without some of the gains we have since obtained in tensile strength”, a- she declared.

“We are finding that after two decades of development in laboratories around the world, this material is working in more and more applications,” Pasquali said. “Due to the combination of conductivity, good skin contact, biocompatibility and softness, carbon nanotube yarns are a natural component for clothing.”

He said the clothing market, although relatively small, could be an entry point for a new generation of sustainable materials that can be derived from hydrocarbons through direct separation, a process that also produces clean hydrogen. The development of such materials is a priority for the Carbon Hub.

“We are in the same situation as solar cells a few decades ago,” Pasquali said. “We need application managers who can provide the pull to increase production and increase efficiency. ”